Hepatitis C is an emerging infectious disease caused by hepatitis C virus (HCV). HCV is a major cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. The outcome of standard treatment is variable and accompanied by significant side effects;new approaches to the prevention and treatment are desperately needed. It has been speculated that a therapeutic vaccine capable of boosting the natural immune response to HCV would reduce the rate at which chronically infected patients progress to cirrhosis and increase the cure rate of patients receiving standard treatment. Currently, however, no vaccine exists. One of the greatest barriers to the development of an HCV vaccine is the genetic diversity found within the virus;multiple genotypes and subtypes (quasispecies) exist. As such, development of an effective vaccine should include strategies to elicit responses to a broad array of likely epitopes and these epitopes should derive from regions of the virus that are relatively conserved across various HCV quasispecies. Therapeutic vaccination with DMA constructs that encode immunodominant, promiscuous and conserved HCV epitopes using dendritic cells as a vaccine adjuvant offers a novel approach to treating chronic hepatitis C. Experiments will be undertaken to: construct a DMA-based vaccine that encodes multiple human HCV epitopes predicted using computational and immunoinformatics tools and validated by demonstrating the response of T cells obtained from young adults previously exposed to HCV (Specific Aim I);demonstrate the ability of dendritic cells transfected with this construct to elicit an immune response in a "humanized" HLA (A2 x DR1)-transgenic mouse model of HCV infection (Specific Aim II);and delineate the factors that effect the HCV-specific response in these vaccinated, transgenic animals (Specific Aim III). The study outlined addresses the critical need to develop and test new strategies to treat HCV infections in a relevant animal model. The results will provide broad insights into the utility of using dendritic cells as a vaccine vector in treatment of other chronic diseases.